Considered to be one of the finest examples of a motte and bailey castle in Kent, Tonbridge Castle has little more than a few fragmentary ruins of its shell keep and curtain walls surviving as a modern-day reminder of the turbulent past it suffered. But Tonbridge Castle's great 13th century gatehouse remains remarkably complete.

Following the Norman Conquest, William granted land at Tonbridge to Richard de Clare (or Fitzgilbert). A timber castle was soon erected on the site and this became the de Clare family home for the next 250 years. Seated high up on top of the impressive mound, the original wooden construction was replaced by a stone shell keep before the end of the 11th century, and was further reinforced during the 13th century, at the same time as the town walls were sanctioned. When the gatehouse was built a few years after Edward I had been lavishly entertained at Tonbridge Castle, his influence was apparent in the layout (which is almost identical to his mighty castle at Caerphilly).

As with many English castles the end of the Civil War effectively signalled the demise of Tonbridge Castle. Orders were given for it to be dismantled, and the ensuing years saw most of it disappear through use as a local quarry. Amazingly the twin-towered gatehouse stood the test of time. This massive stronghold, four storeys high, and faced with ashlar, was defended by a series of portcullises, murder holes, and guardrooms at ground level. Above this were the domestic chambers, and on the next level the main hall once sumptuously decorated and lit by a row of fine traceried windows. When the estate was purchased in 1790, the owner built a Georgian mansion against the east wall of the gatehouse. For the next hundred years Tonbridge Castle passed through the hands of several owners and tenants, it was used as a military academy and as a boys school. The site was finally purchased by the local council in 1900, using the mansion as offices, and opening the grounds as a public park.

Throughout a thousand years of history, Tonbridge Castle has been the subject of much incident, both political and military, and several owners were prone to losing their lives unnaturally. The de Clares were well-known warriors, fighting in many battles during the medieval period. The first Richard was killed during a seige in Normandy, his grandson in Wales, and the last of the heirs died at the Battle of Bannockburn. Then Tonbridge Castle passed to the Stafford family, whose reign ended when Henry was executed by Richard III and his son was executed by Henry VIII in 1520. Meanwhile, Tonbridge Castle had been changing hands between the Crown and its owners.

Resting in peace at last beside the River Medway, the remains of the old castle are scattered throughout the park, and the gatehouse is open to visitors to investigate the troubled times that Tonbridge Castle has experienced.